The present invention is concerned with filtering apparatus and methods and more particularly, such apparatus and methods as are employed to remove suspended solids from a liquid such as in slurry and coal wash water de-watering, sewage sludge removal and other similar industrial processes.
Such applications are required to handle tremendous volumes of liquid and collected solids, and are preferably highly automated for efficient removal of the suspended solids.
One approach heretofore practiced has involved the use of a filtering chamber into which a belt type filtering element is moved to overlie a filtering bed. The filter chamber is sealed and the liquid to be filtered introduced above the belt and pressurized such as to flow through the belt and effect removal of the suspended solids. The filtered liquid is collected at an outlet beneath the belt. Upon a predetermined accumulation of filtered solids or "cake", the filter chamber is unsealed and the belt moved outwardly for removal of the accumulated cake preparatory to initiation of the next filtration cycle, and washing of the belt.
Due to the great volume of liquid typically entailed in such filtering operations, relatively large size filter chambers have been employed which are stacked one atop the other to produce adequate capacity.
In order to effect the sealing and unsealing of the filter chamber, upper and lower halves of the filter housing are separated to enable the filter belts to be moved outwardly after each filter cycle. Since such filter chambers are typically relatively large in size, even moderate filtering pressures produces enormous forces which must be absorbed by the clamping and unclamping mechanism.
The need for separation of the filtering housings in the stack also produces a relatively bulky structure. The clamping mechanism must effect a good seal upon closing of the housing moving together of the housing halves, and must resist considerable pressure in withstanding the hydraulic pressures and to effect a proper seal.
These requirements contribute to the considerable expense of such units. In order to avoid the necessity of the complex, costly mechanical apparatus, it has heretofore been proposed to utilize a tubular flexible seal passing about the opposing housing halves or plates which is inflated or otherwise pressurized in order to effect the seal and deflated in order to unseal the filter chambers.
Examples of this approach are disclosed in U.S. Pat. Nos. 3,899,426 and 3,478,879. However, this approach creates a problem in maintaining the position of the seal while resisting the relatively high hydraulic pressures exerted during the filtering cycle. Also, considerable difficulty is encountered in manufacturing a completely enclosing seal suitable for such high pressure applications.
In filters using a belt type filter element, there is often associated a relatively complex and bulky roller mechanism for receiving relatively long lengths of belt during the removal portion of the machine cycle. It would likewise be highly desirable to simplify this aspect of such apparatus.
Accordingly, it is the object of the present invention to provide a liquid filter apparatus and method of the type including a filter chamber into which is moved a flexible filter medium such as a filter belt, with the filter chamber subsequently sealed prior to the introduction of liquid to be filtered in which the sealing of the chamber is effected by simple and effective means.
It is a further object of the present invention to provide such a filtering apparatus and method which is relatively compact.